support quickcheck test case classification

[bfrk]

When a property test succeeds and QC's classify function has been used, the output now has additional information about the distribution of test cases. Example outputs:

[OK, passed 1000 tests (49.6% fully trivial, 76.1 half trivial)] [Arguments exhausted after 53 tests (100% half trivial)]

The #ifdefs are necessary to account for API changes in version 2.10 and 2.12 of QuickCheck. I was not able to build against QuickCheck < 2.7 because that requires base < 4.8, and the oldest ghc I can install with ghcup is 7.10.3 which is tied to base-4.8.2.0. If you accept this PR and make a new release, I suggest you also raise the lower bound on the QuickCheck dependency to 2.7.

[Bodigrim]

Thanks for your contribution.

AFAICT test-framework is on life support only, the closest descendant in terms of API is tasty.